JP6965015B2 - Image reader - Google Patents

Description

The present invention relates to an image reading device that reads an image formed on a manuscript (hereinafter, referred to as "manuscript image").

An image reading device that reads a document image while moving the scanning unit with respect to the document placed on the document table in the sub-scanning direction can detect the size of the document based on the scanned document image. For example, the image reading device detects a document edge (document edge) from the scanned document image and determines the document size based on the detection result. Patent Document 1 detects the original size in the main scanning direction from the original image read by the scanning unit, and detects the original size in the sub-scanning direction from the detection result of the sensor that detects the presence or absence of the original on the platen. Disclose the device. This device irradiates the original with light and reads the original image in a state where the pressure plate for holding the original placed on the platen is open at a predetermined angle with respect to the platen.

Japanese Unexamined Patent Publication No. 2004-258386

When detecting the original size in the main scanning direction, the presence or absence of the original is determined by comparing the brightness included in the scanning result with a predetermined threshold value, and the original size is determined by the position where the presence or absence of the original changes. Normally, the document holding member provided on the surface of the pressure plate that holds the document is white, and the document is also white. Therefore, when the original is read while the original is held down by the pressure plate, it is difficult to distinguish the presence or absence of the original from the brightness included in the scanning result. A reflective sensor is often used as the sensor (document size detection sensor) used to detect the document size in the sub-scanning direction. In the reflective sensor, it is difficult to distinguish the presence or absence of a document because there is little difference in the amount of reflected light between the document holding member and the document when the pressure plate is closed. From the above, when the document size is detected, the presence or absence of the document is detected with the pressure plate open. That is, the light sources of the reading unit and the document size detection sensor are turned on when the pressure plate is open. In this case, the light from the light source reaches the user's eyes directly. This feels dazzling to the user.

The present invention makes it possible to detect the presence or absence of a document even if the document has an image having a density that does not reflect invisible light while suppressing the glare felt by the user in the document size detection. The purpose is to enable accurate detection of the original size.

In the image reading device of the present invention, a platen on which a document to be read is placed, a pressure plate that can be opened and closed with respect to the platen, and the pressure plate at a first angle with respect to the platen. An angle detecting means for detecting the first state and the second state in which the pressure plate has a second angle smaller than the first angle with respect to the platen, and the document placed on the platen. A reading means having a lighting means for irradiating light and a light receiving means for receiving the reflected light of the irradiated light by the document, and reading the document in the main scanning direction according to the reflected light received by the light receiving means, and the reading means. A sub-scan size detecting means that detects the presence or absence of a document placed at a predetermined position on a platen by irradiating invisible light, and the above-mentioned based on the first detection result and the second detection result by the sub-scan size detecting means. A document size determining means for determining the size of the document according to the sub-scanning size of the document and the main scanning size of the document based on the scanning result by the scanning means, and the lighting means when the pressure plate is in the first state. The lighting means is provided with a control means that does not emit light and causes the lighting means to emit light in response to a change from the first state to the second state, and the first detection result is the first detection result detected by the angle detection means. It is the detection result of the sub-scanning size detecting means obtained according to one state, and the second detection result is the detection result of the sub-scanning size detecting means obtained according to the second state detected by the angle detecting means. It is a detection result, and the second angle is less than 15 °.

According to the present invention, it is possible to detect the presence or absence of a document even if the document has an image having a density that does not reflect invisible light while suppressing the glare felt by the user in the document size detection. , It is possible to detect the document size with high accuracy.

The block diagram of the image reader. The block diagram of the image reader. Explanatory drawing of the platen side of the housing. Explanatory drawing of the control unit. A flowchart showing a document image scanning process including a document size detection process. Explanatory drawing of document edge detection processing. Explanatory drawing of document edge detection processing. A flowchart showing a document image scanning process including a document size detection process.

Hereinafter, embodiments will be described in detail with reference to the drawings.

(overall structure)
1 and 2 are block diagrams of the image reading device of the present embodiment. The image reading device 10 includes a box-shaped housing 101, a document base 102 on which the document A to be read is placed, and a pressure plate 104 to which a document holding member 105 for pressing the document A is attached. The platen 102 is made of a transparent member such as glass. The manuscript A is placed with the side to be read facing the manuscript stand 102 side. The document holding member 105 is configured such that the surface on the side that holds the document A is white so that the outside of the area of the document A does not turn black during scanning. The pressure plate 104 has a variable mounting angle with respect to the housing 101, and is mounted on the housing 101 so as to be openable and closable with respect to the platen 102. The housing 101 incorporates a reading unit 103 for reading a document image from the document A, a control unit 400, and a sub-scanning size detection unit 109.

The reading unit 103 includes illumination units 201a and 201b, reflection mirrors 202a to 202e, an imaging lens 203, a light receiving unit 204, and a sensor substrate 205. The illumination units 201a and 201b irradiate the document A with light. The lighting units 201a and 201b are configured by arranging a plurality of light emitting elements such as LEDs (Light Emitting Diodes) linearly. The reflection mirrors 202a to 202e are optical systems that guide the reflected light from the document A to the imaging lens 203. The imaging lens 203 forms an image of the reflected light guided by the reflection mirrors 202a to 202e on the light receiving surface of the light receiving unit 204.

The light receiving unit 204 outputs an electric signal corresponding to the reflected light received on the light receiving surface. This electric signal is an analog signal representing a document image read from the document A. The light receiving unit 204 is configured by arranging a plurality of photoelectric conversion elements such as a CCD (Charge Coupled Device) sensor in the same direction as the light emitting element array. The light receiving unit 204 is mounted on the sensor board 205. The sensor board 205 is connected to the control unit 400, and transmits an analog signal output from the light receiving unit 204 to the control unit 400. The configuration of the control unit 400 will be described later.

The reading unit 103 having such a configuration reads the original image with the direction in which the light emitting element rows of the illumination units 201a and 201b and the photoelectric conversion element rows of the light receiving unit 204 are arranged as the main scanning direction. The reading unit 103 is attached to the rail 206, and reads the original image while moving on the rail 206. The moving direction of the reading unit 103 is a sub-scanning direction orthogonal to the main scanning direction.

The sub-scanning size detection unit 109 is a reflection type sensor and detects the presence or absence of reflected light from the document A on the document table 102. The presence or absence of the document A can be distinguished from the detection result of the reflected light by the sub-scanning size detection unit 109, whereby the size of the document A in the sub-scanning direction can be detected. The sub-scanning size detection unit 109 irradiates the document A with invisible light, for example, infrared rays, and distinguishes the presence or absence of the document A by the reflected light. Therefore, the user does not feel glare due to the light emitted from the sub-scanning size detection unit 109 even when the pressure plate 104 is in the open state.

The housing 101 includes a pressure plate angle detection flag 106 for detecting the open / closed state of the pressure plate 104 with respect to the document base 102, a first angle detection unit 107, and a second angle detection unit 108. The position of the pressure plate angle detection flag 106 changes due to the opening and closing of the pressure plate 104, and the outputs of the first angle detection unit 107 and the second angle detection unit 108 change. The first angle detection unit 107 is turned on when the angle of the pressure plate 104 with respect to the platen 102 is equal to or less than a predetermined first angle, and is turned off when the angle is larger than the first angle. The second angle detection unit 108 is turned on when the angle of the pressure plate 104 with respect to the platen 102 is equal to or less than a predetermined second angle, and is turned off when the angle is larger than the second angle. The first angle is set to an angle at which the sub-scanning size detection unit 109, which is a reflective sensor, does not erroneously detect the pressure plate 104 as a document, for example, 15 °. The second angle is smaller than the first angle, and is set to an angle at which the light emitted by the reading unit 103 is difficult to reach the user's eyes, for example, 0 °.
The first angle may be another angle such as 20 °, which is larger than 15 °. Further, the second angle may be smaller than 15 ° such as 10 ° or 5 °, and the light emitted by the reading unit 103 may be an angle that is difficult to reach the eyes of a user having an assumed height.

FIG. 3 is an explanatory view of the housing 101 on the platen 102 side. Around the platen 102, a main scanning document size index 301, a sub-scanning document size index 302, and a reference position 303 when the document A is placed are provided. The document A is placed on the document table 102 so that the corners are aligned with the reference position 303. The main scanning document size index 301 is an index of the standard size of the document A placed in accordance with the reference position 303 in the main scanning direction. The sub-scanning document size index 302 is an index of the standard size of the document A placed in accordance with the reference position 303 in the sub-scanning direction. In the example of FIG. 3, an A4 size manuscript A is placed.

The size of the document A in the sub-scanning direction is detected by using the sub-scanning size detection unit 109. The sub-scanning size detection unit 109 is provided between the two standard size indexes in the sub-scanning direction, and detects the presence or absence of the document A on the platen 102. The size of the document A in the sub-scanning direction is detected based on the detection result. In the example of FIG. 3, the sub-scanning size detection unit 109 is provided between the LTR and the B5R, which are two standard size indexes. Depending on the detection result of the presence or absence of the document A in the sub-scanning size detection unit 109 provided at this position, it is possible to distinguish whether the size of the document A in the sub-scanning direction is LTR or less or B5R or more. That is, based on the detection result of the presence / absence of the document A in the sub-scanning size detection unit 109, it is determined whether the size of the document A in the sub-scanning direction is larger than the larger standard size or smaller than the smaller standard size. NS. When the sub-scanning size detection unit 109 is provided at another position, the size of the document in the sub-scanning direction can be distinguished according to the position. Further, by providing a plurality of sub-scanning size detecting units 109 in a row in the sub-scanning direction, more detailed detection of the document size in the sub-scanning direction becomes possible.

The size of the document A in the main scanning direction is detected at the document size detection position. The document A starts scanning from the position of the tip of the document when the document image is scanned. The document size detection position is set at a position separated from the document tip position by a predetermined distance in the sub-scanning direction. The document tip position is the position where the document image is first read when the document A is read.

When the first angle detection unit 107 detects the open state of the pressure plate 104 when the size in the main scanning direction is detected, the control unit 400 moves the reading unit 103 to the document size detection position. After the scanning unit 103 is moved, the control unit 400 reads the document A by a predetermined number of lines while moving the scanning unit 103 from the document size detection position to the document tip position (back scan). The control unit 400 detects the document edge of the document A based on the scanning result by the scanning unit 103, and determines the size of the document in the main scanning direction based on the document edge.

FIG. 4 is an explanatory diagram of the control unit 400. The illumination units 201a and 201b and the light receiving unit 204, the first angle detection unit 107, the second angle detection unit 108, the sub-scanning size detection unit 109, and the motor 406 of the reading unit 103 are connected to the control unit 400. The motor 406 is a drive source for moving the reading unit 103 along the rail 206. The image reading device 10 is connected to an image forming device 40 such as a copying machine, a printer, and a multifunction device.

The control unit 400 is a computer system including a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, and a RAM (Random Access Memory) 410. The CPU 401 controls the operation of the image reading device 10 by reading a computer program from the ROM 402 and executing the RAM 410 in the work area. The CPU 401 controls the operation of the sub-scanning size detection unit 109 and acquires the detection result. In addition, the control unit 400 includes a lighting control unit 403 and a scanning control unit 405 for controlling the operation of the reading unit 103. Further, the control unit 400 includes an A / D conversion unit 407, an image processing unit 408, and a document size determination unit 409 for detecting the document size of the document A. The control unit 400 may be realized by a discrete product or a one-chip semiconductor product. One-chip semiconductor products are, for example, MPU (Micro-Processing Unit), ASIC (Application Specific Integrated Circuit), and SOC (System-On-a-Chip).

The lighting control unit 403 controls the lighting and extinguishing operations of the lighting units 201a and 201b under the control of the CPU 401. In the present embodiment, the lighting control unit 403 lights the lighting units 201a and 201b according to the detection result of the second angle detection unit 108. Specifically, the lighting control unit 403 lights the lighting units 201a and 201b when the second angle detection unit 108 detects that the pressure plate 104 is at least the second angle. The scanning control unit 405 transmits a drive signal to the motor 406 under the control of the CPU 401 to move the reading unit 103 along the rail 206 in the sub-scanning direction at a predetermined speed.

Under the control of the CPU 401, the A / D conversion unit 407 receives an analog signal representing the original image from the light receiving unit 204, converts the analog signal into a digital signal, and transmits the analog signal to the image processing unit 408. The image processing unit 408 performs various image processing on the digital signal acquired from the A / D conversion unit 407 under the control of the CPU 401, and generates image data representing the original image read from the original A. The image data is transmitted from the control unit 400 to the image forming apparatus 40, a personal computer, or the like.

The document size determination unit 409 detects the document edge of the document image based on the image data generated by the image processing unit 408 under the control of the CPU 401, and determines the size of the document A in the main scanning direction based on the detected document edge. decide. The document size determination unit 409 acquires the detection result of the sub-scanning size detection unit 109 via the CPU 401, and thereby determines the size of the document A in the sub-scanning direction. In the example of FIG. 3, when the detection result of the sub-scanning size detecting unit 109 indicates that there is a document, the document size determining unit 409 determines that the size of the document A in the sub-scanning direction is B5R or more. When the detection result of the sub-scanning size detecting unit 109 indicates that there is no document, the document size determining unit 409 determines that the size of the document A in the sub-scanning direction is LTR or less. The document size determination unit 409 determines the document size according to the size in the main scanning direction and the size in the sub-scanning direction of the document.

The CPU 401 detects the angle of the pressure plate 104 from the detection results of the first angle detection unit 107 and the second angle detection unit 108. The CPU 401 detects the document size of the document A by the document size determining unit 409, using the detected angle of the pressure plate 104 as a trigger.

The image forming apparatus 40 includes an image forming unit 411 and an operating unit 412. The image forming unit 411 forms an image represented by the image data on a recording material such as a sheet according to the image data acquired from the control unit 400. The image forming unit 411 forms an image on a recording material having a size corresponding to the original size determined by the control unit 400. As a result, the original image read by the image reading device 10 is formed on a recording material having an appropriate size. The operation unit 412 is a user interface including an input device and an output device. The input device is, for example, various operation keys or a touch panel. The output device is, for example, a display. The operation unit 412 provides information to the user by the output device, and receives an instruction from the user by the input device. The operation unit 412 transmits the received instruction to the control unit 400 and the image forming unit 411. The operation unit 412 may be provided in the image reading device 10.

FIG. 5 is a flowchart showing a document image scanning process including the document size detection process by the image scanning device 10.

The control unit 400 determines whether or not the pressure plate 104 is opened from the first angle or less to an angle larger than the first angle with respect to the platen 102 according to the change in the detection result acquired from the first angle detection unit 107. (S501). The control unit 400 determines that the pressure plate 104 has changed from the first angle or less to the angle larger than the first angle with respect to the platen 102 by changing the detection result of the first angle detection unit 107 from the on state to the off state. do. When the pressure plate 104 is opened at an angle larger than the first angle with respect to the platen 102 (S501: Y), the control unit 400 moves the reading unit 103 to the document size detection position (S502). At this time, the user places the document A on the document table 102 with the corners aligned with the reference position 303. After that, the control unit 400 determines whether or not the pressure plate 104 is closed with respect to the platen 102 from an angle larger than the first angle to the first angle or less based on the change in the detection result acquired from the first angle detection unit 107. (S503). The control unit 400 says that the pressure plate 104 is closed from an angle larger than the first angle to the first angle or less with respect to the platen 102 by changing the detection result of the first angle detection unit 107 from the off state to the on state. to decide.

When the pressure plate 104 is closed below the first angle (S503: Y), the control unit 400 acquires the detection result which is the output of the sub-scanning size detection unit 109 (S504). The control unit 400 determines the size of the document A in the sub-scanning direction based on the detection result of the sub-scanning size detection unit 109 (S505). If the angle of the pressure plate 104 with respect to the platen 102 is the first angle, the invisible light emitted from the sub-scanning size detection unit 109 does not reach the pressure plate 104. Therefore, the sub-scanning size detection unit 109 does not erroneously detect the pressure plate 104 as the document A immediately after the pressure plate 104 is closed at the first angle or less.

The control unit 400 that determines the size in the sub-scanning direction acquires from the second angle detection unit 108 whether or not the pressure plate 104 is closed from an angle larger than the second angle to a second angle or less with respect to the platen 102. Judgment is made according to the change in the detection result (S506). The control unit 400 says that the pressure plate 104 is closed from an angle larger than the second angle to a second angle or less with respect to the platen 102 by changing the detection result of the second angle detection unit 108 from the off state to the on state. to decide.

When the pressure plate 104 is closed at a second angle or less (S506: Y), the control unit 400 lights the illumination units 201a and 201b of the reading unit 103 (S507), and moves the reading unit 103 from the document size detection position to the tip of the document. Move to position. As a result, the control unit 400 performs a back scan of the document A to read a predetermined number of lines (S508). By back-scanning, the control unit 400 acquires analog signals representing a predetermined number of lines of original images from the reading unit 103. Since the pressure plate 104 is closed at the second angle or less, the glare of the light of the illumination units 201a and 201b felt by the user is suppressed to the minimum.

The control unit 400 converts an analog signal representing the acquired original image into a digital signal by the A / D conversion unit 407, and the image processing unit 408 processes the analog signal to generate image data. The control unit 400 detects the document edge in the main scanning direction of the document A by the document size determination unit 409 based on the image data (S509). The details of the document edge detection process will be described later. The control unit 400 determines the size of the document A in the main scanning direction based on the detected document edge (S510). The control unit 400 determines the document size of the document A according to the size of the document A determined in S505 in the sub-scanning direction and the size of the document A determined in S510 in the main scanning direction (S511).

The control unit 400 that determines the document size controls the operation of the scanning unit 103 to read the document image of the document A placed on the document table 102 (S512). After placing the document A on the document table 102, the user operates the operation unit 412 to instruct the image reading device 10 to read the document image. The operation unit 412 transmits an instruction to read the original image to the control unit 400 in response to the user's operation. The control unit 400 starts reading the original image by acquiring an instruction for reading the original image from the operation unit 412.
By the above processing, the original size of the original A placed on the platen 102 is determined, and the original image is read. The image data representing the scanned original image is sent to, for example, the image forming apparatus 40, and is used by the image forming unit 411 for the image forming process on the recording material.

6 and 7 are explanatory views of the document edge detection process of S509. The document size determination unit 409 of the control unit 400 determines whether or not the document edge is a document edge for each pixel of the document image, and detects the document edge. The control unit 400 accurately detects the document edge even if dust, hair, or other dust is attached to the document holding member 105 as follows.

The document size determination unit 409 uses three determination formulas to determine whether or not the pixel of interest to be determined for the document edge is a pixel of the document edge (manuscript edge pixel). The position of the pixel of interest in the main scanning direction is "x", and the brightness value of the pixel of interest is "f (x)". The brightness value for each pixel is included in the image data. In the first determination formula, the brightness values f (x + H1) and f (x-H1) of the pixels at two positions (x + H1), (x-H1) separated by a predetermined first distance H1 in the main scanning direction from the pixel of interest. It represents the luminance difference value g (x) which is the difference value of.
g (x) = f (x + H1) -f (x-H1)

The second determination formula represents a difference value h (x) between the maximum luminance value and the minimum luminance value of a pixel within a predetermined second distance H2 larger than the first distance H1 in the main scanning direction from the pixel of interest. ..
h (x) = max (f (x-2H), ..., f (x), ... f (x + H2))
-Min (f (x-2H), ..., f (x), ... f (x + H2))

The third determination formula represents an average value i (x) of the brightness values of pixels within a predetermined third distance H3 in the main scanning direction from the pixel of interest.
i (x) = ave (f (x + 3H), ..., f (x), ... f (x-H3))

The document size determination unit 409 determines whether or not the pixel of interest is a document edge pixel by comparing the calculation results of the first to third determination formulas with the first to third threshold values, respectively.

The light emitting elements of the illumination units 201a and 201b illuminate the document A at an angle. Therefore, a shadow is generated on the edge of the document due to the thickness of the document A. Due to this shadow, a difference in brightness is generated between the document edge and the document holding member 105. The luminance difference value g (x) is calculated to detect this luminance difference. The first threshold value TH1 is set to a value at which the brightness value due to the document edge and the brightness value due to the document holding member 105, which is the background, can be distinguished. At the document edge, the absolute value of the luminance difference value g (x) is larger than the first threshold value TH1, and at the portion of the document holding member 105 that is not the document edge, the absolute value of the luminance difference value g (x) is smaller than the first threshold value TH1. .. The first threshold value TH1 is set in consideration of a document having a small basis weight in which shadows are unlikely to occur.

The document size determination unit 409 can separate white streaks by changing the sign of the luminance difference value g (x). Since the shadow of the document edge has a lower brightness than the surrounding pixels, the sign of the brightness difference value g (x) changes from plus to minus when viewed from the outside in the main scanning direction. Since the white streaks have higher brightness than the surrounding pixels, the sign of the brightness difference value g (x) changes from minus to plus when viewed from the outside in the main scanning direction. The document size determination unit 409 cuts out white streaks by changing the sign. As described above, the luminance difference value g (x) can be used to separate the document edge from the document holding member 105 and the white streaks. However, the brightness difference value g (x) becomes large even when dust such as dust and hair is read. Therefore, it is difficult for the document size determination unit 409 to separate the pixels when the dust is read from the document edge due to the luminance difference value g (x).

The document size determination unit 409 compares the difference value h (x) with the second threshold value TH2 to separate the pixels when dust is read from the document edge. There are often differences in the characteristics of brightness between the shadows caused by the edges of the document and the shadows caused by dust. The shadow generated by the edge of the document becomes blurred due to the influence of the diffused light of the illumination units 201a and 201b. The shadows created by the dust are often darker than the shadows created by the edges of the document. Therefore, the brightness value of the shadow generated by the dust is lower than the brightness value of the shadow generated by the edge of the document. That is, the difference value h (x) in the range including the shadow due to the document edge is smaller than the difference value h (x) in the range including the shadow caused by dust. Therefore, the cause of the shadow can be determined by distinguishing the difference value h (x) by an appropriate second threshold value TH2. The second threshold TH2 is set to such a value. However, with the luminance difference value g (x) and the difference value h (x), the document size determination unit 409 may erroneously detect the document edge of a black document having no margin as dust such as dust or hair. ..

By comparing the average value i (x) with the third threshold value TH3, the document size determination unit 409 determines the document edge of the black document having no margin by the average value i (x) and the pixels when dust is read. Carve out. When the document A is a black document with no margins, the average value i (x) of the brightness values of the pixels within a predetermined range in the main scanning direction near the document edge is the average value i (x) when the brightness value due to dust is included. ) Is smaller than. This is because the average value i (x) includes a large amount of the luminance value of the original edge of the black original. The dust is often small dots or streaks, and when the brightness values are averaged over a wide range to some extent, the influence of the dust becomes small, and the average value i (x) includes a large amount of the white brightness value of the document holding member 105. .. Therefore, when the brightness value due to dust is included, the average value i (x) becomes large. By distinguishing such an average value i (x) by an appropriate third threshold value TH3, the cause of the shadow can be determined. The third threshold TH3 is set to such a value.

The document size determination unit 409 distinguishes whether or not the pixel of interest is a document edge pixel by performing a combination of determinations based on the luminance difference value g (x), the difference value h (x), and the average value i (x). Can be done accurately. Further, as shown in FIG. 7, the document size determination unit 409 counts the number of document edge pixels in a plurality of lines in the sub-scanning direction to suppress the influence of noise and improve the document edge detection accuracy. Can be done. When there are a plurality of document edge positions detected by the document edge detection, the document size determination unit 409 sets the outermost position as the document edge position. This reduces the possibility that the figures and ruled lines in the document A are erroneously detected as document edges.

In FIG. 7, the document edge is detected by the count number of the candidate pixels of the document edge. Candidate pixels for the original edge are determined in the main scanning direction. By repeating the process for N lines, it becomes possible to determine whether or not a predetermined number or more of pixels at the same position in the main scanning direction exist in the candidate pixels of the document edge in the sub-scanning direction. This predetermined number is the fourth threshold value TH4. In the example of FIG. 7, there are seven candidate pixels for the document edge in the eighth pixel from the left end in the main scanning direction. Therefore, it is determined that the eighth pixel from the left end in the main scanning direction is the document edge. The third pixel, the 14th pixel, and the 16th pixel from the left end in the main scanning direction have candidate pixels for the document edge, but are not determined as document edges because they are less than a predetermined number (fourth threshold value TH4). In this way, even if dust that may be erroneously detected in the one-line processing is generated, the influence thereof can be suppressed and the document edge can be detected with high accuracy.

FIG. 8 is another flowchart showing the document image scanning process including the document size detection process by the image scanning device 10. Since the processes of S801 to S804 are the same as the processes of S501 to S504 of FIG. 5, the description thereof will be omitted.

The control unit 400 determines whether or not the pressure plate 104 is closed at a second angle or less with respect to the platen 102 based on a change in the detection result acquired from the second angle detection unit 108 (S805). The control unit 400 says that the pressure plate 104 is closed from an angle larger than the second angle to a second angle or less with respect to the platen 102 by changing the detection result of the second angle detection unit 108 from the off state to the on state. to decide. When the pressure plate 104 is closed to the second angle or less (S805: Y), the control unit 400 acquires the detection result which is the output of the sub-scanning size detection unit 109 (S806). The control unit 400 determines the size of the document A in the sub-scanning direction based on the detection result of the sub-scanning size detection unit 109 acquired in the processes of S804 and S806 (S807). After that, the control unit 400 determines the document size of the document A and reads the document image of the document A by executing the processes of S808 to S813 similar to the processes of S507 to S512 of FIG. The image data representing the scanned original image is sent to, for example, the image forming apparatus 40, and is used by the image forming unit 411 for the image forming process on the recording material.

For a document having an image having a density that does not reflect invisible light used by the sub-scanning size detection unit 109 for detection, the presence or absence of the document may be erroneously detected. Regarding such a document, in the process of FIG. 8, the control unit 400 of the sub-scanning size detecting unit 109 of the sub-scanning size detection unit 109 at the timing when the pressure plate 104 becomes the first angle or less and the timing when the pressure plate 104 becomes the second angle or less with respect to the platen 102. Acquire the detection result. The control unit 400 detects that there is a document if the two detection results are the same, and detects that there is no document if the two detection results are different. By doing so, even if the original has an image having a density that does not reflect invisible light, the presence or absence of the original can be accurately detected and the size of the original in the sub-scanning direction can be determined.

Specifically, in the case of a document in which an image having a density of reflecting invisible light is formed, the sub-scanning size detection unit 109 is used when the angle of the pressure plate 104 with respect to the platen 102 is either the first angle or the second angle. Even if there is, the presence of the document is detected in order to receive the reflected light from the document. In the case of a document in which an image having a density that does not reflect invisible light is formed, the sub-scanning size detection unit 109 may perform the sub-scanning size detection unit 109 regardless of whether the angle of the pressure plate 104 with respect to the platen 102 is the first angle or the second angle. , Detects the presence of a document because there is no reflected light from the document. When the original is not placed, the control unit 400 has no original because the angle of the pressure plate 104 with respect to the platen 102 is the first angle and there is no reflected light from the original, and the second angle is the reflected light from the pressure plate 104. Detect.

The image reading device 10 having the above configuration determines the size of the document A in the main scanning direction and the sub-scanning direction according to the open / closed state of the pressure plate 104 when the document size is detected. Since the sub-scanning size detecting unit 109 for detecting the size in the sub-scanning direction detects the presence or absence of the original using invisible light, the user does not feel dazzling regardless of the open / closed state of the pressure plate 104. In the reading unit 103 for detecting the size in the main scanning direction, the illumination unit 201 does not irradiate the light unless the pressure plate 104 is at least the second angle with respect to the platen 102. Therefore, the user's feeling of dazzling is minimized.

The configuration for detecting the open / closed state (angle) of the pressure plate 104 with respect to the platen 102 is not limited to the configuration including the pressure plate angle detection flag 106, the first angle detection unit 107, and the second angle detection unit 108. Any configuration may be used as long as it can detect the first angle and the second angle of the pressure plate 104 with respect to the platen 102. For example, the first angle detection unit 107 and the second angle detection unit 108 may be configured by one sensor, and the output of the sensor may be changed according to the amount of change in the position of the pressure plate angle detection flag 106.

Claims (5)

The platen on which the document to be scanned is placed and
A pressure plate that can be opened and closed with respect to the platen
Angle detection for detecting the first state in which the pressure plate is at the first angle with respect to the platen and the second state in which the pressure plate is at a second angle smaller than the first angle with respect to the platen. Means and
It has an illuminating means for irradiating a document placed on the platen with light and a light receiving means for receiving the reflected light of the irradiated light by the document, and the document is subjected to the reflected light received by the light receiving means. A reading means that reads in the main scanning direction,
A sub-scanning size detecting means that detects the presence or absence of a document placed at a predetermined position on the platen by irradiating it with invisible light.
The size of the document is determined according to the sub-scanning size of the document based on the first detection result and the second detection result by the sub-scanning size detecting means and the main scanning size of the document based on the scanning result by the scanning means. Manuscript size determination means and
The pressure plate is provided with a control means that does not cause the lighting means to emit light in the first state, but causes the lighting means to emit light in response to a change from the first state to the second state.
The first detection result is a detection result of the sub-scanning size detecting means obtained according to the first state detected by the angle detecting means.
The second detection result is a detection result of the sub-scanning size detecting means obtained according to the second state detected by the angle detecting means.
The second angle is less than 15 °.
Image reader. The sub-scanning size detecting means is a reflective sensor.
The angle detecting means has a first angle at which the sub-scanning size detecting means does not erroneously detect the pressure plate on the document, and an angle at which the light emitted by the reading means is difficult to reach the user's eyes. It is characterized by having a second angle,
The image reading device according to claim 1. The sub-scanning size detecting means is provided between two standard size indexes in the sub-scanning direction, and the document size determining means is in the sub-scanning direction of the document according to the detection result of the sub-scanning size detecting means. Is characterized in that it is determined whether the size of is larger than the larger standard size or smaller than the smaller standard size.
The image reading device according to claim 1 or 2. The sub-scanning size detecting means are provided side by side in the sub-scanning direction.
The document size determining means determines the size of the document in the sub-scanning direction according to the detection results of the plurality of sub-scanning size detecting means.
The image reading device according to any one of claims 1 to 3. The document size determining means has the brightness of two pixels separated by a predetermined first distance from the pixel of interest at a predetermined position in the main scanning direction from the reading result of the document of a predetermined number of lines read by the scanning means. The first difference value of the value and the second difference value between the maximum brightness value and the minimum brightness value within a range separated by a second distance larger than the first distance from the attention pixel are calculated, and the first difference value is calculated. It is determined whether or not the pixel of interest is a document edge based on the difference value of 1 and the second difference value, and if it is the document edge, the size of the document is detected according to the position of the pixel of interest. Characteristic,
The image reading device according to any one of claims 1 to 4.

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